The invention relates to a method and to a switching arrangement for changing a switching state of a switching half-bridge which has two field-effect transistors from a first switching state, in which a first field-effect transistor is switched on and the second field-effect transistor is switched off, to a second switching state, in which the first field-effect transistor is switched off and the second field-effect transistor is switched on.
The invention in particular relates to a method and to a switching arrangement for changing a switching state of a switching half-bridge which has two “WBG” field-effect transistors (WBG=wide-bandgap). A WBG field-effect transistor is taken to mean a field-effect transistor, the base material of which is a semiconductor with a wide bandgap (=energy gap between the valence band and conduction band) such as silicon carbide or gallium nitride. Due to their lower switching losses in comparison with the bipolar transistors with an insulated gate electrode (IGBT) which are frequently used, WBG field-effect transistors are in particular advantageously suitable for improving the power density of power converters such as pulse-controlled inverters or DC-DC converters. The switching frequency may thus be appreciably increased while maintaining identical switching losses, as a result of which the size of passive components in the system such as filters, transformers and link capacitors may be reduced.
At high switching speeds, parasitic repowering up of the field-effect transistor may occur when a field-effect transistor of a switching half-bridge is switched off. This effect is also known parasitic switching back on or “self turn-on”, Due to a capacitive displacement current, the gate-source voltage between gate and source of the field-effect transistor which is being switched off is here briefly raised above the threshold voltage of the field-effect transistor, whereby the field-effect transistor becomes conductive again. This results in greatly increased switch-off losses of the field-effect transistor which is being switched off and switch-on losses of the complementary field-effect transistor which is being switched on of the switching half-bridge.
The object of the present invention is to provide a method and a switching arrangement for changing a switching state of a switching half-bridge which has two field-effect transistors, which method and arrangement are improved in particular with regard to avoidance of parasitic switching back on during switch-off of a field-effect transistor of the switching half-bridge